The role of implantable medical devices to treat disorders of the heart, brain, nervous system and musculoskeletal system is increasingly becoming a major part of therapy and has been facilitated due to recent advances in technology. Diseases that disrupt the heart, brain, or nervous system's ability to communicate or function normally include heart rhythm disorders such as ventricular fibrillation which could be life threatening, heart block, and neurologic disorders such as epilepsy, multiple sclerosis, spinal injury, and dysautonomias. Pharmacologic therapy had traditionally been used to treat these disorders along with the use of pacemakers and defibrillators to treat heart rhythm disorders.
The treatment of brain and nervous system disorders includes deep brain stimulation methods that involve placing wires within the brain and attaching them to an implantable device to stimulate the target areas of the nervous system in order to control epilepsy, hypertension, as well as movement disorders such as Parkinson's disease. Surgical procedures have further been proposed for these disorders. For example, open brain surgery for the placement of leads (wires) that are positioned through brain tissue to reach the target sites and tunneled under the skin to a device implanted elsewhere, as well as placing wires in the heart to provide a defibrillation shock (established procedure) using the blood vessels as a conduit to reach the heart.
The treatment of epilepsy has traditionally been limited to medications or aggressive brain surgery to remove affected areas responsible for the seizures. In many ways, epilepsy has characteristics that are shared with ventricular fibrillation of the heart. Both disorders are associated with an abrupt disturbance of a regular (normal) electrical rhythm resulting in chaotic electrical activation of the heart or brain which in turn causes a seizure or sudden cardiac death.
However, current technologies, such as those described in U.S. Pat. Nos. 6,412,490 and 5,987,352, are hampered by the use of non-biological sensing elements such as electrodes or imaging based sensing. Complex steps and subsequent inherent risks are involved in obtaining venous vascular access and placing a transvenous lead in the patient population requiring defibrillation. In addition, when neurologic treatment requires an implantable lead, problems associated with lead infection, extraction when infected, as well as the mode of reaching the target organ with the least amount of trauma are important considerations.